PubMed Health⌕ Search

Biomedical subjects

L L Katalymov

Publications and source records attributed to L L Katalymov.

At least 19 recordsLinked to original sources
PubMed2004

[Postcatelectrotonic potentials and trace changes in the nerve fiber excitability].

When cathode subthreshold impulse was turned off, excitable membranes of isolated nerve fibres and nervous trunk show postelectrotonic depolarisation (PED), that is a slow recovery of membrane potential to the resting level. PED of the single nodes of Ranvier and nervous trunk is registered not only in normal conditions, but also after complete block of sodium channels. The size and duration of nervous trunk PED under subthreshold depolarising current increase along with duration of applied depolarisation: when cathode current 1 ms in duration was used, they were 0.093 +/- +/- 0.004 mV and 7.123 +/- 0.576 ms, respectively; when current was 5 ms in duration, they were 0.189 +/- 0.005 mV and 23.212 +/- 1.186 ms, whereas a 10-ms depolarisation yields values of 0.220 +/- 0.011 mV and 68.721 +/- 3.389 ms. Application of the train of catelectrotonic impulses leads to PED built-up. As PED is found not only in normal conditions but also after complete block of sodium channels, it is reasonable to suggest that the most probable reason for PED is an outward potassium current.

Action Potentials↗
PubMed2001

Effect of exogenous nitric oxide on electrogenesis in myelinated and unmyelinated nerve fibers.

Extracellular recording was used to study the effect of sodium nitroprusside, a donor of NO, on parameters of action potential and ionic currents in single sciatic nerve fibers and unmyelinated nerve terminals in the sternal muscle in frogs. Sodium nitroprusside significantly decreased the duration of action potential in Ranvier node and the amplitude of afterdepolarization. In motor nerve terminals bathed in low Ca(2+) saline, sodium nitroprusside increased phase III amplitude of the nerve terminal response corresponding to outward potassium currents. Blockade of voltage-dependent potassium channels with 4-aminopyridine abolished the effects of NO. These data indicate that exogenous NO reduced the duration of action potential and afterdepolarization through enhancement of voltage-dependent potassium currents.

Action Potentials↗
PubMed1981

[Increase in the after-depolarization of a single node of Ranvier of isolated nerve fibers after application divalent (Ca2+, Ba2+, Mn2+, Zn2+, Ni2+) and trivalent (La2+) ions].

It has been shown that a 5.5-fold increase in Ca2+ concentration in the external solution leads to the rise in negative after depolarization (NAD) of a single node of Ranvier of myelinated nerve fibres isolated from Rana ridibunda. The NAD amplitude and duration increase 1.3-fold and 1.6 fold, respectively. Introduction in the external solution of Ba2+ and Mn2+ (up to 10 mM) leads to a negligible increase in NAD. A more pronounced effect on action potential and NAD of the node of Ranvier is exerted by Zn2+ and Ni2+ (1.5 and 10 mM), entailing a 5-fold and 10-fold increase in NAD duration. Combined action of Ni2+ and tetraethylammonium brings about a depolarization plateau lasting 50-150 ms followed by the development of NAD lasting 14-30 ms. Introduction in the external solution of La3+ produces a 3--7-fold increase in NAD. Under all exposures cited the decrease in NAD in exponential in character, as is the case in normal Ringer's solution. The changes in NAD described are likely to be accounted for by the effect of the ions on the time constants of the processes of activation and inactivation.

Action Potentials↗
PubMed1980

[Effect of changes in the external concentration of sodium, chlorine, and potassium ions on subsequent depolarization of a single node of Ranvier of isolated nerve fibers].

Change in external concentration of Na+ (from 0 to 240 mmol), Cl- (from 0 to 120 mmol), and K+ (from 2.5 to 10--30 mmol) had no significant effect on the negative trace potential in the Ranvier isthmus of Rana ridibunda. In K+-free Ringer's solution a trace hyperpolarization occurred. The negative trace potential of the isthmus increased in blockade of the membrane potassium channels with tetraethylammonium chloride or 4-aminopyrydine.

Aminopyridines↗
PubMed1978

[Effect of CO2 on the excitable membrane of a single node of Ranvier].

Introduction into the chamber containing the preparation of a gaseous mixture with a 5% CO2 content failed to lead to any significant changes in the recorded parameters of the node of Ranvier. Elevation of CO2 concentration to 50% caused a significant increase of resistance, of the critical level of the membrane depolarization, a decrease of the spike amplitude, and of the maximum steepness of its increase. Two minutes after the beginning of the gas mixture introduction spike degeneration stopped. CO2 action was completely reversible. The trace potentials of the node of Ranvier remained unchanged with the CO2 action in the mentioned concentrations.

Animals↗
PubMed1978

[Confirmation of the hypothesis concerning the existence of a diffusion barrier in the region of the nodes of Ranvier of myelinated nerve fibers].

It was shown that during rhythmic stimulation of the node of Ranvier in the potassium-free solution there was an exponential decline of the trace hyperpolarization. This is attributed to the fact that potassium ions released from the fiber during the activity collect in the premembranous space separated from the external solution by diffuse barrier.

Animals↗
PubMed1976

[The effect of changes in the pH of the external solution on the afterpotentials of individual frog nodes of Ranvier].

A decrease in pH to 5 elicited a small increase in afterdepolarization of a single Ranvier node and an increase in pH to 9 had no effect. Post-tetanic hyperpolarization decreases at pH 5 and its duration somewhat increases. An increase in pH to 9 also had no effect. Similar changes in afterdepolarization and post-tetanic hyperpolarization were observed in potassium free solutions. A conclusion is made that changes in afterpotentials are determined by changes in kinetics of the membrane potassium permeability.

Action Potentials↗
PubMed1975

[Post-tetanic hyperpolarization of lake-frog isolated nerve fibers].

Posttetanic hyperpolarization (PTH) parameters of a single node of Ranvier remained unchanged with increase of the stimulation duration of over 0.1 sec. PTH was insensitive to strophanthin, but was eliminated by tetraethylammonium. Resistance of the membrane of node of Ranvier measured by the amplitude of anode impacts proved to be lovered during the PTH by 50%. A conclusion was drawn that PTH of the isolated nerve fibers was caused by the persistence of increased potassium permeability during and after the end of tetanus. An increase in duration of tetanization failed to lead to the appearance of PTH associated with active ion transport.

Animals↗